Expansion pocket for dowel bars



July 12, 1949. F.o. HELTZiEL v 2,473,243

v EXPANSION POCKET FOR DOWEL BARS Filed Nov. 29,- 1945 F" .4 66 24 AME?12 Fig.5

awe/whom Francis QHeli' eZ wk; I? l 06, 12 mvmww Patented July 12, 1949UNITED STATES PATENT OFFICE 4 Claims.

The invention relates to expansion and contraction joints for concretepaving construction, and more particularly to an expansion pocket fordowel bars for sustaining in alignment separately formed adjacentsection: of the paving.

Highways and similar paving, especially when constructed of concrete,are formed in sections or slabs, and it is common practice to leave aspace between the adjacent edges of the slabs, which space is filledwith a compressible material which will permit expansion of the concreteslabs and consequent compressing of the packing material withoutresulting injury to the slabs.

It is customary to join these slabs so that they will not becomedisplaced and permit one slab to sink below the surface of another andthus cause an uneven road surface, and the usual method is to placetransload dowel bars at frequent intervals which extend about half intoone slab and half into an abutting slab.

When the pavement becomes heated the slabs will expand and upon coolingthe slabs will contract. This working of the slabs sometimes placesconsiderable shearing strain on the dowel bars making it necessary thatthe ends of the dowel bars must not be restricted against movement. Itis thus necessary that the ends of the dowel bars not be restrictedagainst movement, or at least one end of each dowelbar be free to moveinto the adjoining slab as expansion occurs.

For this reason it is common practice to place an expansion cap upon oneend of each dowel bar, the type of expansion cap most commonly usedconsisting of a thin metal cylinder with closed end and one or moreindentations or stops. It frequently occurs that too tight a fit isprovided causing the cylinder to expand and destroying the same as anexpansion cap.

It also happens that the cylinder is driven onto the dowel bar beyondthe stop thereby causing seepage of cement and loss of expansion.

The object of the present improvement is to provide an expansion pocketfor the dowel bars which are provided for the necessary expansion andcontraction of adjacent slabs of cement and to permit room for the endsof the dowel bars to move into and out of the expansion pocket duringthe relative movement of the concrete slab.

Another object is to provide an expansion pocket which will overcome thedifficulties and disadvantages of present practice.

A further object is to provide a sealed dowel expansion pocket whichprevents the seepage of cement into the pocket.

A still further object of the invention is to provide an expansionpocket comprising a box of sheet metal or the like adapted to fit uponone end of the dowel bar and having a shaped insert, formed of sheetmetal or the like, normally acting as a stop to position the boxrelative to the dowel bar but capable of being pushed into the box whenexpansion occurs.

Still another object is to provide such an expansion pocket in which theshaped insert is provided with ears or wings at its side edges normallyengaged in grooves or channels at the side edges of the box, the dowelbar being of I-shape so that when the shaped insert is pushed into thepocket by expansion the ears or wings thereof will be forced along theweb of the dowel.

The above objects, together with others which will be apparent from thedrawing and following description or which may be later referred to, maybe attained by constructing the improved expansion pocket in the mannerhereinafter described in detail and illustrated in the accompanyingdrawing, in which;

Figure 1 is a transverse section through an expansion joint between twoadjacent slabs of concrete, showing a dowel bar located therethrough andprovided with the improved expansion pocket;

Fig. 2 a detached perspective view of the improved expansion pocket;

Fig. 3 a front end elevation of the expansion pocket;

Fig. 4 a fragmentary, sectional view showing one end portion of a dowelbar with the improved expansion pocket mounted thereon;

Fig. 5 a section taken as on the line 55, Fig. 4; and,

Fig. 6 a view similar to Fig. 5 showing the manner in which the shapedinsert is pushed into the expansion pocket when expansion takes place.

The dowel bar, indicated generally at ID, to which the improvedexpansion pocket is applied, is preferably of substantially I-shape incross section, as shown in my prior Patent No. 2,309,- 767, issuedFebruary 2, 1943, and comprises the upper and lower flanges ll,connected by the web 12.

Each dowel bar may be supported upon a chair which may be formed from asingle length of strap iron, wire or the like and may comprise thehorizontal base portion l3, the upright forward leg M formed at theforward end of the base portion, the upright rear leg I5 formed at therear end of the base portion and the forwardly disposed horizontalportion [6 at the upper end of the rear leg, a pin or stake l1 beingdriven through suitable apertures in the chair and into the roadfoundation or base to anchor the chair in position. Tie rods 18 may bewelded or otherwise attached to the chair for connecting several similarchairs of each joint together.

The chair supports one end portion of the dowel bar It within the endportion of a concrete slab it), the other end portion of the dowelextending into the adjacent edge portion of an abutting concrete slab20, the dowel bar being located through suitable openings in theremovable joint strip 2| and the premolded joint 22, which may be formedof any usual and well known compression material, such as an asphalt orbitumen composition, as in ordinary practice.

The improved expansion pocket to which the invention pertains is mountedupon the end portion of the dowel bar which is located within theconcrete slab 2D and may comprise a sheetmetal rectangular box shapedmember indicated generally at 23. The side walls of this box-shapedmember are equi-distantly recessed from the open end thereof, so thatthe upper and lower portions of the box are continued above and belowsaid recesses as upper and lower channel portions 24, upper and lowerwalls respectively of which are preferably .of double thickness as bestshown in Figs. 2, 3 and 4, adapted to slidably receive the upper andlower flange portion ll of the :dowel bar, and preferably having theflared outer ends 25. v

The primary object for forming these upper and lower walls of doublethickness-is to provide flexibility .to accommodate variations in thesize of the dowel bars, commonly known as mill-tolerance, and at thesame time provide a perfect seal against grout seepage.

The side walls of the box 23 at the ends of said recesses are providedwith the grooved or channel flanges 26 which receive the-ears or wings21 formed upon the shaped collapsible closure insert plate 28, of sheetmetal or similar material.

As shown quite clearly in Figs. 1, 2 and 4 to 6 of the drawings, thechannel portions 24 extend a considerable distance beyond the insertplate 28 at the-open end of the box.

When the expansion pocket is placed upon the end of thedowel bar, asshown in Figs. 1', 4 and 5, it contacts the end of the dowel bar actingas a stop to position the expansion pocket thereon.

In practice the structure is set up in the manner illustrated in Fig. 1and above described and with the parts of the structure in thisposition, the concrete forming the slabs 1 9 and 20 is poured,completely enclosing the structure in the roadway as shown in Fig. 1. Asthe material of the slabs sets, the entire structure will become bondedto the slabs except the end of the dowel bar located in the slab 2Bwhich will be free to slide in the expansion pocket 23.

Upon expansion of the slabs the free end of the dowel bar will be forcedinto the box portion of the expansion pocket pushing the shaped insert28 therein and bending the ears or wings 2! as they are forced out ofthe grooves or channels 26, these ears or wings being accommodated uponopposite ends of the web portion 12 of the dowel bar as shown in Fig. 6.

Upon further expansion the dowel bar will move further into the box ofthe expansion pocket and upon contraction of the slabs the end'of thedowel bar-will of course move out of said box.

From the above it will be seen that a simple, inexpensive and eflicientexpansion pocketis provided which overcomes the objections anddisadvantages of present practice and will not permit seepage of cementand consequent loss of expansion, and that the shaped insert provides aperfeet seal and a fool-proof stop for perfect expansion.

I claim:

1. An expansion pocket for use in connection with a dowel bar that ispositioned between ex pansible members, said expansion pocket comprisinga rectangular box-shaped member open at its inner end, the side wallsthereof being equidistantly recessed from :the open end thereof so thatthe upper and lower portions of the box above and below said recessesform channels for slidably receiving the adjacent end portion of the anda collapsible closure plate having ears detachably connected to saidflanges to normally close the open ended the box and provide a stop forcontact with the end of the dowel bar.

2. An expansion pocket for use in connection with a dowel bar that ispositioned between expansible "members, .said expansion pocket:comprising a rectangular box-shaped member of oblong cross section openat its inner end, the side walls thereof being \equi-distantly recessedfrom the open end thereof so that the upper and lower portions of theboxabove and below said recesses form channels for slidably'receivingthe adjacent end portion of the dowel bar, flanges at the ends of saidrecesses and .a collapsible closure plate havingears detachablyconnected to said flanges to normally close :the open end of the box andprovide a stop for contact with the end of the dowel bar.

.3. An expansion pocket for use in connection with a dowel bar that ispositioned between expansible members, said expansion pocket comprisinga rectangular box-shaped member open at its inner end, the side wallsthereof being equidistantly recessed from the open end thereof so thatthe upper and lower portions of the box above and below said recessesform channels for slidably receiving the adjacentend portion of thedowel bar, the ends of said channels being flared, flanges at the endsof said recesses and a collapsibleclosure plate having ears detachablycon nected to said flanges to normally close the open end of the :boxand provide a stop for contact with the end of the dowel bar.

4. An expansion pocket for use in connection with a dowel bar that ispositioned between expansible members, said expansion pocket comprisinga rectangular box-shaped'member formed of sheet material and open at itsinner end, the side walls thereof being equi-distantly recessed from theopen end thereof, so that the upper and lower portions of the box aboveand below said recesses form channels for slidably receiving theadjacent end portion of the dowel bar, the sheet material being lappedat the top and bottom of the box to provide a double thickness extendingthe entire length of the box, flanges at the ends of said recesses and acollapsible closure plate having ears detachably connected to saidflanges to normally close the open end of the box and provide a stop forcontact with the end of the dowel bar.

FRANCIS O. HELTZEL.

REFERENCES CITED The following references are of record in the file ofthis patent:

2,149,396 Klein Mar. 7, 1939 2,181,623 Klein NOV. 28, 1939 2,255,599Olmsted Sept. 9, 1941 2,410,099 Olmsted et a1. Oct. 29, 1946

